ARM: dts: aspeed-evb: Add unit name to memory node

Fixes a warning when building with W=1.

All of the ASPEED device trees build without warnings now.
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-ast2500-evb.dts

@@ -16,7 +16,7 @@ chosen {
 		bootargs = "console=ttyS4,115200 earlyprintk";
 	};
 
-	memory {
+	memory@80000000 {
 		reg = <0x80000000 0x20000000>;
 	};
 };